Automatic telephone system



G. A. YANo'cHowsKl. AUTOMATIC TELEPHONE SYSTEM.

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TTO/P/VF Y G. A. YANOCHOWSKI.

AUTOMATIC TELEPHONE SYSTEM.

l APPLICATION FILED APR.10, |916. 1,847,069. wanted July 2o, 1920.

2 SHEETS-SHEET 2.

MTA/55555 w/E/VTQR:

FQ MATITA?? UNITED STATES PATENT OFFICE.

YGfEOItGrnI/i, YANoCIioWs-KI, or CHICAGO,v ILLInoIs, nssIGivOR` ToAUTOMATIC ELECTRIC CQMPANY, or CHICAGO, TLLIIOIs, A CORPORATION OFILLINOIS.

AUTOMATIC TELEPHONE sYsTn'M.

Application filed April 10, 1916.

To @Zlio/0m 1i/map' Concern! y 'Y leit known that I, Gro-non AQYANooI-Iowsin, a citizen oit the United States of America, and aresident oi Chicago,` county ,of Cook, and State ot Illinois, haveinvented certain new and useful improvements in Automatic rtelephoneSystems, ot' Vwhich the following is a speciica'tion..

VMy invention relates to automaticV telephone systemsand moreparticularly to those automatic systems which are commonly rinown as,two-wire, systems, so called by reason of the iact that the' automaticswitches are Controlled over the two sides oi the line in series,exclusive of ground at the subscribefs station.

ln systems or' the above general character it has been the commonpractice to control the release and the switching of the' local circuitsof the automatic switches through the medium of a combination ot' quickand slow acting relays. More specificallyfa slow acting relay may beprovided responsive to a prolonged interruption of the line circuit tocontrol the release, while a'. second slow acting relay may be providedresponsive to a ltime interval between series ot impulses to control theswitching.

The object of my invention'is to provide an automatic system in whichthe control ot 'the releasing'and switching functions does not dependexclusively upon a time element, thereby avoiding to a considerableextent the use of slow acting' relays.

The particular means employed in attaining the foregoing ends and theoperation thereoi will be fully described hereinafter, reiference beinghad to the accompanying drawings, in which Figures l and 2, when alten'in order with the lines at the ends thereoiQ in alinement,represent.,diagram` .f'cally a complete circuit connection be'- n acfing substation ri. anda called tion` It in a system embodying theciples oit my invention. The said connection has been establishedvthrough the,

medium ot the idividual line switch C, selector switch E, and connectorH.Y Fig. 3 is a detail oi" a portion ofthe dial mechanisni.

Referring now toFig. l, the subscribers substation .et be or" anysuitable type and comprises the usual receiver 2, transmitter Sfringe'rand' condenser 5. Being an automatic substationit is also provided withsuitable impulse sending device somei. Specification of Letters Patent.

Patented July 20, 1920 serial No. 90,047.

what similar to that shown in British Patent No, 29,654- ot 1910 to S.G. S. Dicker, except that two extra impulse Vsprings are added,together' with means for controlling the same. The impulse sending`device comprises a pair of impulse springs G and 7, and an auxiliarypair of impulse springs 9 and l0, which are assumed to be controlledthrough the medium of a finger hole dial (not shown) in suoli a mannerthat the impulse springs G and 7 may be momentarily separated a numberof times corresponding to the digit called, followed by a group ot highspeed impulses or interruptions transmitted bythe impulse springs 9 andll). These highspeed impulses are similar to the impulses transmitted bythe impulse springs 6 and l but are at a much greater speed, or in otherwords, they consist ot one or more interruptions or impulses at a highfrequency, as lcompared to the impulses transmitted by the impulsesprings (l and 7. Referring to Fig. 5, it will be seen that to therotatable portion ll of the dial, there is secured a pawl l2, one endoi2 which is held in normal position against the pin 13 by a spring le'.lllhen the dial is rotated in a clockwise direction (which is in acounter clockwise direction as seen in Fig. 3),the pawl l2 strikes thespring 9 in such a inan- `ner as to tilt the said pawl downward, thusallowing it to pass the spring 9 without causing it to break contactwith the spring l0. But when the dial is released and the rotatableportion ll rotates back to normal, one or more impulses are transmittedover the line conductors by means ot impulse springs 6 and T, then, justbefore the dial has returned to normal position, the pawl l2 engages thespring` 9 and bends itdowne ward until the pawl 1Q, has passcdbeyond thesaid spring. Then the pawl l2 releases the spring 9, the said springv'ibrates for a instant and br alrs Contact several times with springl0, sending one or more quick or high frequency impulses'.

'lie hoolt switch 16 in addition vto controlling the usual hook switchsprings 1T, 18 and i9. also controls the springs 20, 2l,

. TO and 7l.l The springs 2() and 2l are constructed similar to thesprings 9 and l0, that is, when the receiver is removed from the switchhook, the pawl 72 `on arm 22 attached to the hook switch lever i6operates to tilt downward an nisses the sprh 2O and 2l without separating their Contact, v

but whenpthe receiver is placed upon the hook switch, the arm 22,invlowering, bends the spring 2O downward, after which and as soon asthe spring 2O slides off the arm 22, a number of high speed impulsesYare the said impulse springs, then the springs 20 qand 21 operate asherein described and lastly the springs 17 and 18 separate to` open theline circuit. The subscribers'individual switch C is of the general typeof lineswitch shown in British patent to R. lV. James ;l;t26,301 of`1906, and similar to the type 'of switch shown Vin British Vpatent to T.Gr.v Martin #1419 `oi 1910, the circuits being slightly modified,

however.l This line switch comprises, among other details, a plunger(not shown) Vattached to the end of a so-called plunger arm 23, which iscontrolled by the magnet 24.: The magnet 24 comprises two windings,namely, the pull-in winding 25 and the holding or cut-ofi' winding 26.The winding 25 operates both the plunger arm v23 and theV cut-ori1armature 27 while the windv ing V26 is only strong enough to-operate thearmature 27 and toV hold the plunger arm 23 in an operated positionafter it hasV once been operated bythe pull-in winding 25. 'l'he circuitof the pull-in winding 25r is controlled by the line relay 2S andtheauxiliary'V relay 29, 'both of which preferably, make slow acting, thatis, they are slow to denergize after their energizing circuit has beenbroken. Vhen the plunger n arm 23 is operated, theplunger is forced intoa bank of contact springs, forcing the springs 30, 31, 32 and 33 intoengagement with springs 34, 35, 36 and 37, respectively. Although onlyone set of springs (30-37) is shown, each line switch is provided with aplurality of such sets, each set forming the terminal of a trunk line'leading to a selector switch E. Ylach trunk line is connected Vinmultiple to. the lcorresponding springs of all the switches of the'group which is controlled by the master switch D.

The master switch i) 'is of the same gen- Y eral type as that disclosedin British Patent #26,301 above referred to; being, however,

of the'particular type disclosed in saidBritish Patent .#1419 of 1910.The function Y of the'inaster switch, as is wellknown, is

Vto maintain the plungers of all the idle line switches in position toengage the terminal of an idle trunk line.

The irst selector E 1s of theV same general type oi' selector switchdisclosed -in the United VStates Letters VPatent jr-,5815,331, granted`March 13, 1906 to Keith, Erickson, and Erickson except that theso-called side switch is dispensed with and the circuits are modifiedinaccordance with my invention to adaptV the switch to operate in asystem in whichcontrolling impulsesare delivered over the two sides ofthe lineY in series. Among other details, the selector E comprises abank Vof contacts arranged in horizontal rows or levels, which lcontactsare adapted to be engaged by a set of wipers 38, 39 andf40 carried upona shaft (not shown) which has a verticalmovement con- 80 trolled ,by thevertical magnet 41 and a Y rotary movement controlled bythe rotaryVmagnet 42'. The operations or various parts of the switchv arecontrolledV through the medium of the double wound line relay 43. Meansvfor permitting'the switch to be restored to normal position is providedin the release magnet 44, which, uponenergizing, vwithdraws `theretaining double-dog from the shaft thereby allowingthev shaft andwipers tobe-restored to their normal position.. The contacts 45and 46close only when the switch-shattlias been raised one or more steps fromits lowest position. Thev Y contact spring 47 (controlled by the arma--95 ture 48 of line relay 43) is so constructed and adjusted as tofollow up the spring 49 when thenrelay43 is energized. Should one orkmore impulses vbetransmitted..through the line relay 43, as ordinarilyproduced byV the operation of the impulse springs 6 and 7, the springs47 and 49 will operate in unison and fremainl in contact, but shouldhigh speed impulses be transmitted to the line relay by means oftheimpulse springs 105 v9 andlO or the releasesprings 20 and 21, the

springs 47 and 49 willbe separated for anV instantbecause the spring 47,by V'reason of the inertia of theweight at its extremity, isY unableto'follow. '.1 11( The connector switch H' (Fig.l 2) is of the lgeneralztype vof connector switch disclosed in United States LettersPatent #815,17 6 granted March 13, 1906, to Keith, Erickson,

vand Erickson; the circuits, however, being modified in vaccordance withthe same principles followed in the design of the selector Like. theselector, the connector is provided with a' shaft `(not shown) carryingthe l wipers 55, 56, and,57,'and controlled by the 12( verticalmagnet'53 Vand the rotary magnet 54. The usual sideY switch comprisingthe wipers 50, 51, 52, vand 59 is controlled 'by the private magnet 58in the usual andV well `known. manner. The Vmagnet 60 is the usual 12:

release magnet. -The relay 62 is the back bridge Yrelay whichfurnishestalking batteryto the called subscriber. The springs 63 and 64controlled by the line relay 61 operate in Y the same manner ashereinbet'ore 13( described in the case of the springs 47 and 49 of theselector E. The contacts 65, 66, and 67 close only when the shaft hasbeen raised one or more steps from its lowest position, while thecontact 68 closes only when the shaft has been rotated one or more stepsfrom its normal position. AThe relay 69 is the means through whichringing current isV applied to the called line. y The substation shownat A and the line switch C are similar in all respects to the lineswitch C and the substation A.

F or the purpose of supplying battery current ior operating theapparatus at the central exchange and for talking purposes, thereisshown the battery B having its positive terminal grounded. At Q there isshown a busy signaling machine which provides a busy signal forapplication to the calling line when the called line is in use.

Havingl given a general description of the vapparatus and in order togive a clear understanding of the operation of the system, it will nowbe described in detail how the calling subscriber at substation A mayobtain connection with the subscriber a't the called substation A. 7ewill assume that the number of the called substation is 229. Upon theremoval of the receiver at the substation A, a circuit is closed throughthe line relay 28 of line switch C. This V.circuit extends from groundG2 through contact springs 73, conductor 75, to and through thesubstation A, conductor 76, springs 74 and the line relay 28 to batteryB. The line relay 28, upon energizing, operates to close the circuit' orthe pull-in winding 25. This circuit extends from ground G through thesprings 66, springs 67 and 68, pull-in winding 25 and the springs 69 tobattery B. The pull-in winding 25 operates to disconnect the line relay28k from the line through the medium of cut-oli armature 27, and toforce the plunger into thev bank of contacts (B0- 37). The line relay 28being slow acting, does not fall back immediately, however, but holdsthe plunger arm in an operated position until aV Vholding ground issupplied to the holding winding 26 from the selector E. The engagementof' springs 30 and 33 with the springs 34 and 37, respectively, extendsthe subscribers line to the Vline relay43 of the selectorrlil. The linelrelay 43 of the selector :switch E is thereupon energized, therebyclosing a circuit through the relay 78, it beingnoted, that spring 47follows spring 49 all the way so that springs and 77 come intoelectrical connection atthe same time. The circuit for relay 78 extendsfrom ground G3 through contact springs 77, 49, and 47 springs 7 9 andthe relay'7 8 to the battery B. The relay 78, upon energizing, closesthe above mentioned holding circuit through the cut-oil1 winding 26Ofiline switch C. This circuit extends from ground G4' through thesprings 80, bank contact 35 and spring 31 and the said cut-oil winding26 to battery B. A guarding potential is supplied to the connectorprivate bank contacts of the calling line by the energization of relay29. The energizing circuit for the relay 29 may be traced as a branch ofthe holding circuit from spring 31, through springs 81 and the relay 29to battery B.

A further result of the energizing of line relay 43 is the closure of acircuit through the relay 82. This circuit extends from ground G3through the springs 77 and 49, the upper winding of said relay 82 andthe springs 83 to battery B. The relay 82, upon energizing, forms alocking circuit for itself,

extending from ground G5 through the springs 85, the lower winding ofrelay 82 and the springs 83 to battery A further result oiE theenergizing of ,relay 82 is to close a circuit through the relay 86. Thiscircuit extends from ground G5 through the springs 88 and 87 and thesaid relay 86 to battery B. Further results of the energizing of relay82 a-re the preparation of a circuit or the vertical magnet 41 byclosing lthe springs 89 and 90, and the opening oi the circuit of therelease magnet 44 at the springs 90 and 91. The apparatus is now 'inreadiness to receive impulses for the first digit. f

- 1f the calling subscriber should now replace his receiver upon thereceiver hook the switch hook upon descending would cause the springs 20and 21 to operate in a hereinbefore mentioned manner to ytransmit one ormore high speed interruptions or impulses. lThe relay 48 will vibrateits armature in response to the said impulses, with the resul-t that thesprings 47 and 49 are separated for an instant at this time because thespring 47 has a slower natural period of vibration Vthan the spring 49.It may vbe mentioned here that the rapid vibrations of the line relay 43do not `affect the vertical magnet to any extent, for the closure ofvsprings 97 is extremely short. The separa- .lay' 82 at springs 83, thusallowingV the said relay 82 to denergize; and as soon as the switch hookhas separated the switch hook springs 17 and 18 the line relay 43denergizes and opens the circuit oit the relays 94 and 78. The relay 78,upon dener,g'izing,

opens the circuit of the holding winding 26 of line switch C at thesprings-80. The hold` ing winding, upondenergizing, permits the plungerarm of lineswitch C to return to normal;

- responding tothe two impulsessentv by the impulse springs 6 and 7operates to transmit two impulses of current through the vertical magnet41. This circuit extends from ground GG through contact springs 97,springs 98, springs and 89 and the vertical magnet 41 to battery B. They,vertical magnet receiving two impulses over this circuit operates toraise the shaft and wipers .of selector E two steps to apositionopposite the second row or level of bank contacts. ATheclosureof the off-normal contact 46, which occurs when the selectorshaft is raised, operates to close a locking circuit for the relay 36over a path extending from ground G4 through the contact springs S0,

springs V99, off-normal contact46, springs 103'.and 104 and the saidrelay S6 to battery B. The ,high speed interruptions at` the springs 9Aand 10 that follow thetwo impulses just transmitted by the impulsesprings 6 and 7, cause the'line relay 43 to Vvibrate quickly.-Asheieinbefore stated the result is that the springs 47 and 49 are se 5varated for an instant thusrallowingthe relay 94 to energize overapreviously-traced circuit. The relay 94, upon energizing, opens thecircuit of the relay 82 at the springs 33 and permanently removes theshunt from around itself at springs 79. The de'nergizing of relay4 82closesV a circuit through the rotary magnet 42over the tollowing path:ground G4, contact springs 8 0,

springs 99, contact 46, springs 103 and 104,

springs S7 and 105, springs 101 and the rotary magnet'42 to battery B.Trie rotary Vmagnet, upon energizing, rotates thewipei's `one step'and,by separating the springs 99 and the springs 101, opens its own circuitand also the circuit of relay 86. Tf therst trunk line of the secondlevel is idle, the relay 86 denergizes immediately, but if this trunkline is busy, the private wiper 39 finds the contact with which itengages provided with a guarding groundV potential, which is transmittedto the relay 86 .through the springs 103 and 104, thereby preventing itYfrom denergizing. The rotary magnet, however, denergizes .when thesprings 101 separate, regardless oi' whether therelay 86 lremainsenergized or not. lf the relay 86 Vremains energized, the circuit of therotary magnet will be again closed as soonV as the armature drops backfar enough to close the springs 101. The rotary magnet will, therefore,operate in a Vinanneisimilar to that of af buzzer to advance the wipersstep by step over the contacts until the non-guarded con-'f tact of anidle trunk line is reached by the f wiper 39whereupon the relaySGrle'energiz'es. YThe relay V86, upon dene'rgizing, whether aiter oneor several operations of the rotary magnet,permanentlybrealrs thecircuit of the'magnet42 andcloses the cir-V cuit of the switching relay106. VThe circuit through said relay 106 extends from ground Gr4 throughthe contactspringsSO, springs 99, contact 46, springs 103and 102 and theswitching relay 106 to battery B. The re'- v'lay106, upon energizing,extends the line connection throughthe wipers 3S and 40 to the linerelay 61 oit connector H anddis- 'connects the line'relay 43 from thesaid call- The line relay 61, upon energizing, closes i a circuitthroughthe relay 110. This circuitpextends from ground GS through theY springs111 and 64, lower windingI otrelay 110, springs 112, springs 114,Vsprings 115,

Yand the side switch wiper 59 first posi,

tion)` to battery B. The relay 110, upon energizing, closes a lockingcircuit'tor itself through the springs '116, and prepares acircuit forthe vertical magnet by bringing the springs 118 r and 119Vintoengagement. A further result of the energization of Ythe line vrelay61 is' theclosure of a circuit vthrough vthe relay 120. This circuitextends from ground GS throughfthey springs 111, 64, and 63, springs 113andthe 'relayv 120 to battery B. The relay 120,` upon energizing, sup-Vplies a holdinggroundtothetrunk release conductor 103i to hold the relay106 of Ase lector E and winding 26 of line Vswitch .0, energized. f Thiscircuit extends from ground VG9 through Athe ,springsV 121, springs 122,

124, where theV circuit divides, onebraneh extending through the springs103 and 102 and vthe relay 106 toi battery B, andthe other branchextending lfrom' point 124 through the oi'-`iiormal contact,;46, springs99,`banlr contact 35 springs31and the holding winding 26 to battery B.

place hisreceiver upon the receiver hook the switch hook upon descendingwould cause the springs 20 and 2 1 to'operate` in a hereinbefore`mentioned manner to transmit one or more l high speed interruptions orimpulses. VThe V'line relay 61 will respond to the said impulses Y' andas hereinbeto're lstatedthe result is that the springs 63 and 64 areseparatedtor an instant at this time because thespring 63A Vconductor10S, wiper 39V to wire junction f .ll4 Tt the callingsubscriber shouldnowrehas al slower natural periodV ot Vvibration thantlie spring-64. Theseparation of the springs 63 and 64 for an instant allows the relay toenergizeby removing the shunt VJfrom around the said relay. The .energiah ing circuit for relay 125 extends from ground GS through the springs111 and 6.4, relay 1.25, and the. relay 120 to battery B.. The relay125, upon energizing, opens the shunt from. around itselrat' the springs113, opens the circuit of relay 110 at springs 11,2, and closes acircuit through the. private magnet 58 overa circuit extending fromground G11 through the contact springs. 127, 12.8, and 129, magnet 58and the side switch wiper 59 (in lirst position) to,` battery B. Assoonv as the receiver hook has descended far enough to open the circuitof line relay 6l, thesaid relay willr denergize. The line relay, upondenergizing, opens the circuit of relays 125 and 120 at springs 64 and111. The relay 125, upon denergizing, opens the circuit of the privatemagnet 5S, at the springs 127, 128 and 129; but the private magnet, upondenergizing, does not trip the side switch to second position'as theside switch cannot advance to second position until the switch shaft hasbeen raised one or moreV steps from. its lowest position as shown in thepatents abovereferred to. The re lay 120, upon denergizing, removes theground: from the trunk release conductor 1:08 at the springs 121, thus.allowing the relay 106 of selector E and holding coil 26 of line switchC to denergize. The line switch (l releases in the hereinbeforementioned: manner. The relay 106, upon deenergizing, closes a circuitthrough the release magnet 44. This circuit extends from ground Gr6through the springs 97, springs 98, springs 90 and. 91, release magnet44 and the oflnormal contact 45 to. battery B.. The release magnet, uponenergizing, withdraws the retaining double-dog from the shaft and theswitch releases in a well known manner.

Assuming that the calling subscriber did not replace his receiver atthis time, but that he operates his dial for the second digit 2 of thecalled number, the substation impulse springs. 6 and 7 are separatedtwice, tollowed by high speed impulses transmitted by. the impulsesprings 9 Yandv 10. The line relay 61 responding to the two. impulsessent by the impulse springs 6 `and 7 operates to transmit two impulsesthrough the vertical magnet 53. This circuit extends from ground G13through the springs 130, springs 118 and 119, the vertical 1nagnet53,and the side switch wiper 51 (in rst position) to battery B. Thevertical magnet, upon receiving the two impulses over this circuit,opcrates to raise the shaft and wipers two steps to a position oppositethe second row or level of bank contacts. The high speed interruptionsthat tollow'the two impulses just transmitted by the impulses springs 6and 7 cause the line rel-ay 61 to vibrate quickly. As hereinbeforestated the result is that the springs 63 and 64 are separated for aninstant, thus allowing the relay 125 to energize over a hereinbeiioretraced circuit. rlhe relay 125, upon energizing, closes aY circuitthrough the private magnet 58 and opens the circuit of the relay 110.The relay 110, upon denergizing, shunts out the relay 125 over a circuitextending from ground (is through the springs 111, 64 and 63, off-normalcontact 65, and springs 1.3.1 to one terminal of relay 125, the otherterminal being connected to ground G8 over a hereinbefore tracedcircuit. rlhe relay 125, upon denergizing, causes the private magnet 53to advance the side switch to second position and again closes thecircuit of relay 110 at the springs 112, The springs 113 and 112 otrelay 125 are so adjusted that the relay 125, upon denergizing, againplaces a shunt around itself before the circuit of relay 110 is closed.The side switch wiper 51 moving' from lirst to second positiontransfersthe battery connection from the vertical magnet 53 to therotary magnet 54. i

The apparatus is now in readiness to receive impulses for the thirddigit 0. If the calling subscriber should now replace his receiver hook,the springs 2O and 21 will operate in a hereinbefore described manner totransmit one or more high speed impulses which cause the line relay 61to respond to said impulses and to operate relays 125 and 110, ashereinbefore described. TheA relay 125 operates to close a circuitthrough the private magnet and the release magnet 60.

vThe private magnet is unable to advance the side switch from second tothird position, because, as is well known, the side switch ismechanically locked in second position until the switclrshatt has beenrotated one or more steps from normal. The circuit through the releasemagnet extends from ground G1V1 through the springs 127 and 128, sideswitch wiper 50 in second position, rotary olf-normal Contact 68,release magnet 60 and the vertical off-normal Contact 67 to battery B.The release magnet, upon energizing, closes a locking circuit foritseliCv through the springs 134, and oil'- normal contact 66 to G16and, restores the switch shaft and side switch wipers to normal positionand its own circuit is broken at the contacts 67 and 66 when the switchshaft reaches its lowest position. The relay 120, being slow acting,will dcnergize a short time after its` energizing circuit is broken bythe line relay 61. The relay 120, upon denergizing, removes the groundfrom the trunk release conductor 108, allowing the selector E and lineswitch C to release as hereinbefore described.

Assuming that the calling subscriber did not replace his receiver uponthe receiver hook, but that he operates his dial for the last digit 0,the substation impulse springs 6 and 7 are separated ten times followedby high speed impulses transmitted by the imi Y pulse springs 9 and 10.The line relay 61 responding to the ten impulses sent by the impulsesprings 6 and 7 operates to trans-A Y the relay 125 to operate toclose acircuit Vline.

through the piivatemagnet 58 and to open i the circuit ofV the relay 110at the springsV 112. The relay 110, upon denergizing, again places ashunt around the relay'125, thus causing the relay 125 to denergize,which causes` the private magnet to deiinergize and advance the sideswitch to third position. IThe circuit of the relay 110 is again closedat the springs 112 when the relay 125 denergizes but the said relay doesnot energize at vthis time as its circuit was opened at the side switchwiper 59 when it passed from second to third position. The opening ofthe rotary off-normal springs 68 Vprevents the release magnet 60 frombe-A ingenergized4 when the relay 125 is energized at this time. Theside switch wiper 52,'upon passing to third position closesa circuitthrough the cut-oit winding 186 or" line switch C, and the relay 138ofconnector HL A further result of the Vpassing otside switch wiper' 52to third position. is the placing oit a guarding potential upon themultiple bank contacts ot the called The eneigization of the relay 13Scompletes the line connection troni the call ing to the calledsubscribersline. VThe side 'switch wiper 51 upon passing from second tothird position closesV a circuit through the ringer relay 69. Thiscircuit extends from ground G15 through the interrupter 139, ringerrelay `69, springs 140 and the side switch wiper 51 (in third position)to battery B. The ringer relay 69, upon energizing, disconnects thecalling line from the called line and bridges the ringing currentgenerator R across the called line. The ringer relay 69 is energizedintermittently through the medium ot' the interrupter 139. Upon theresponse of the called subscriber his line is providedrwith talkingbattery through the windings of the back bridge relay 62, ,which relay,upon energizing, closes-a circuit through the ringer cut-oit y relay142. This circuit extends from ground G16 through off-normal contact 66,springs V143, (relay 142 and the side switch wiper 51 (in thirdposition) to battery B. The

The highY Ysignal from his own individual line switch.

' converse without lfurther eort. The transmitter at the callingsubstation issupplied with' talking current through the windings of thedouble-wound relay V61, "while the transmitter at the called'substationis supplied with talking current through the 'windings of thedouble-wound relay The path for Vvoice currents hasbeen drawn in heavylines and Ywill Abe apparent without further explanatiom f v After the.conversation isV completed, the connection is released by the `hangingup or the receiver at the calling substation in the tollowingcmanner:The connector is released by theopening of the switch hookY springs 17and 18, which opens the circuit ot' the connector line relay 6l.y Theline relay 61', upon denergizing, closes a circuit through the releasemagnet 60 and opens the circuit of the relay 120 at springs 111 and 64.The circuit for the release magnet extends from ground Glthrough thesprings 130, springs 118 and 117,7release'magnet 60 and theoitnormalcontact 67V to battery B. Upon the closure ot the abovecircuit, the connector releases in the manner previously described. Therelay 120, iipon denergizing, removes the holding ground G9- rom therelease conductor 10S, allowing the selector E and line switch C torelease ashereinbetore described.

It havingbeen explained how one sub seriber establishes Connection withanother subscriber and releases the saine, it will new be explained howa. connection is prevented from being made with a-busy line, how thecalling automatic switches are released, and

how the calling subscriber receives a busy T the called number is busythere will be a guarding potential uponthe connector private bankcontact, justas explained in cen nection with line switch C. Theconnector private wiper 56, upon engaging this guarding contact and whenthe privatemagnet' energizes, a circult is closed through the busy relay145. This circuit extends trom ground upon the private Vbank contactthrough the wiper. 56, side switch wiper 52 .(in 'second position), busyrelay 145, and the springs 146 ot private magnet 5S, to battery B. Therelay 145, upon energizing, closes a locking circuit for itself throughthercontacts 147 independent of the private magnet 5S, re-

moves the ground from the release conductor 108 at springs 122, andopens the circuit or relay 110 at springs 114. The removal et' theground from the said conductor 108 causes the plunger of the line switchC to be withere drawn from its bank of contacts and the selector .E tobe released as hereinbefore described. The cut-off arm 27 and plunger'arm 23 dropping back allow the circuit of the line relay 28 to beclosed. The relay 28, upon energizing, closes a locking circuit throughthe relay 29, which being slow acting has not denergized. The relay 29maintains the circuit of the pullin Yinding open at the springs 68 and(3.7. A further result of the energization of the line rela-y 28 is thesupplying of a busy tone from the machine Q, to the calling line throughthe contact of its springs 14S. The opening of the line circuit of theconnector I-I at the bank spr'n gs 30, and 33 causes the line relay 61to deenergize. The line relay 61, upon deenergizing, causes theconnector II to release as hereinbefore described. The callingsubscriber upon receiving the busy signal replaces his receiver upon thereceiver hook and releases relays 28 and 29 of the line switch C,whereupon all the apparatus will `have been returned to normal.

t will be seen from the foregoing that my invention provides anautomatic telephone system, in which the local, switching, at thevarious automatic switches is accomplished entirely through the mediumof a device responsive to high frequency impulses while irresponsive tothe preceding operating impulses; and it will be seen, furthermore, thatat certain times the release of the automatic switches is brought aboutdirectly or indirectly in response to similar righ frequency impulsestransmitted -by the subscribers switch hook.

lllhile I have illustrated and described herein a certain particularembodiment of my invention, I do not wish to be held to the exact formshown, for modifications will no doubt be devised by persons skilled inthe art. I desire, therefore, to include and have protected by LettersPatent all forms and modifications of my invention which may come withinthe scope of the appended claims.

W'hat I claim as my invention is:

l. In a telephone system, an automatic progressively movable switch, acontrolling circuit for said switch including the two sides of a callingline in series, an operating magnet and a release magnet for saidswitch, means for transmitting a plurality of impulses of one characterover said controlling circuit to control said operating magnet, andmeans for transmitting a plurality of impulses of a dierent characterover said controlling circuit to control said release magnet.

2. In a telephone system, an automatic progressively movable switch, acontrolling circuit for said switch, an operating magnet and a releasemagnet for said switch,

means for transmitting impulses of low and high frequency over saidcircuit, a relay in said switch responsive to said low frequencyimpulses for controlling said operating 1 L. `ne anc a re a in sait swici res onmag t, l l l tl sive to said high frequency impulses forcontrolling said release magnet.

E3. In a telephone system, an automatic progressively movable switch, acontrolling circuit for said switch, an operating magnet and a releasemagnet for said switch, means for transmitting low and high frequencyimpulses over said circuit, a relay in said switch for controlling saidrelease magnet, and a line relay in said switch responsive to said lowfrequency impulses for controlling said operating magnet and responsiveto said high frequency impulses for operating said first relay torelease said switch.

4L. In a telephone system, a line terminating in an automaticprogressively movable switch, means at the substation on said line fortransmitting groups of operating impulses of one frequency and a groupof releasing impulses of a different frequency to said switch over saidline, said switch provided with operating means responsive to said groupof operating impulses, and releasing means responsive to said group ofreleasing impulses.

5. In a telephone system, a substation telephone instrument and a lineltherefor eX- tending to a central Xchange, an automatic switch, means atthe exchange for making said switch accessible to said line, means insaid instrument for sending directive impulses over said line to operatesaid switch, means controlled by the receiver hook of said telephoneinstrument for sending a group of high frequency impulses over saidline, and means responsive to said last impulses for releasing saidswitch.

(5. In a telephone system, an automatic progressively movable switchprovided with operating means and releasing means, and a commoncontrolling circuit therefor, said means separately responsive toimpulses of different frequency transmitted over said controllingcircuit.

7. vIn a telephone system, a calling subscribers line, means includingan automatic switch for extending said line into connection with acalled line, means at the substation on the callingline for producinglong and short interruptions of the line circuit for controlling saidswitch, operating mechanism in said switch responsive to said longinterruptions, and release mechanism in said switch responsive to saidshort interruptions.

Signed by me at Chicago, Cook county, State of Illinois, this th day ofApril, 1916.

GEGRGE A. YANOCHOVSKI.

